This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below, after the main part of the detailed description section.
Printed wiring boards (PWBs, also referred to a printed circuit boards, PCBs, or also as boards in this document) are boards having multiple layers. A PWB mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched typically from copper sheets laminated onto a non-conductive substrate. Usually one or both of the top and bottom layers have the electronic components on them, like microprocessors, memory chips, capacitors, inductors, amplifiers, and the like. The inner layers typically have ground, power, and/or signal routing. Such boards have been used for electronics for many years and basically any electronics (such as smartphones, laptops, personal computers, tablets, televisions, receivers, etc.) contain such PWBs.
The electronic components attached to the boards can create high temperatures in the PWB. At the moment, we only measure temperature with few external temperature sensors and get only spot temperatures of the boards. Furthermore, there is no method of producing a thermal image of the board when there is no line of sight to the board, such as when the board has a cover, a heat sink, or the like blocking the direct view to enable thermal imaging of the board. Thus, some of the hot spots in the board, in both the research and development phase and in the field, are not found with the current method, and consequently many boards are released having less than ideal temperature profiles. Every component has a certain operating temperature range, and by violating this range, there will be a dramatic decrease in the life time of the component. Even if the component's temperature stays in the “approved” operating range, a higher temperature means a reduced lifetime, especially for capacitors. Furthermore, exceeding the allowed environmental temperature range may cause overstressing of wire bonds, thus tearing the connections loose, cracking the semiconductor dies, or causing packaging cracks. Humidity and subsequent high temperature heating may also cause cracking, as may mechanical damage or shock to components weakened by excess heat.